The Collaborative International Dictionary of English v.0.48:

Hydrostatic \Hy`dro*stat"ic\, Hydrostatical \Hy`dro*stat"ic*al\,
   a. [Hydro-, 1 + Gr. ? causing to stand: cf. F. hydrostatique.
   See Static.]
   Of or relating to hydrostatics; pertaining to, or in
   accordance with, the principles of the equilibrium of fluids.
   [1913 Webster]

         The first discovery made in hydrostatics since the time
         of Archimedes is due to Stevinus.        --Hallam.
   [1913 Webster]

   Hydrostatic balance, a balance for weighing substances in
      water, for the purpose of ascertaining their specific
      gravities.

   Hydrostatic bed, a water bed.

   Hydrostatic bellows, an apparatus consisting of a
      water-tight bellowslike case with a long, upright tube,
      into which water may be poured to illustrate the
      hydrostatic paradox.

   Hydrostatic paradox, the proposition in hydrostatics that
      any quantity of water, however small, may be made to
      counterbalance any weight, however great; or the law of
      the equality of pressure of fluids in all directions.

   Hydrostatic press, a machine in which great force, with
      slow motion, is communicated to a large plunger by means
      of water forced into the cylinder in which it moves, by a
      forcing pump of small diameter, to which the power is
      applied, the principle involved being the same as in the
      hydrostatic bellows. Also called hydraulic press, and
      Bramah press. In the illustration, a is a pump with a
      small plunger b, which forces the water into the cylinder
      c, thus driving upward the large plunder d, which performs
      the reduced work, such as compressing cotton bales, etc.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hydraulic \Hy*drau"lic\, a. [F. hydraulique, L. hydraulicus, fr.
   Gr. ?, ?, a water organ; "y`dwr water + ? flute, pipe. See
   Hydra.]
   Of or pertaining to hydraulics, or to fluids in motion;
   conveying, or acting by, water; as, an hydraulic clock,
   crane, or dock.
   [1913 Webster]

   Hydraulic accumulator, an accumulator for hydraulic
      machinery of any kind. See Accumulator, 2.

   Hydraulic brake, a cataract. See Cataract, 3.

   Hydraulic cement, a cement or mortar made of hydraulic
      lime, which will harden under water.

   Hydraulic elevator, a lift operated by the weight or
      pressure of water.

   Hydraulic jack. See under Jack.

   Hydraulic lime, quicklime obtained from hydraulic
      limestone, and used for cementing under water, etc.

   Hydraulic limestone, a limestone which contains some clay,
      and which yields a quicklime that will set, or form a
      firm, strong mass, under water.

   Hydraulic main (Gas Works), a horizontal pipe containing
      water at the bottom into which the ends of the pipes from
      the retorts dip, for passing the gas through water in
      order to remove ammonia.

   Hydraulic mining, a system of mining in which the force of
      a jet of water is used to wash down a bank of gold-bearing
      gravel or earth. [Pacific Coast]

   Hydraulic press, a hydrostatic press. See under
      Hydrostatic.

   Hydraulic propeller, a device for propelling ships by means
      of a stream of water ejected under water rearward from the
      ship.

   Hydraulic ram, a machine for raising water by means of the
      energy of the moving water of which a portion is to be
      raised. When the rush of water through the main pipe d
      shuts the valve at a, the momentum of the current thus
      suddenly checked forces part of it into the air chamber b,
      and up the pipe c, its return being prevented by a valve
      at the entrance to the air chamber, while the dropping of
      the valve a by its own weight allows another rush through
      the main pipe, and so on alternately.

   Hydraulic valve. (Mach.)
   (a) A valve for regulating the distribution of water in the
       cylinders of hydraulic elevators, cranes, etc.
   (b) (Gas Works) An inverted cup with a partition dipping into
       water, for opening or closing communication between two
       gas mains, the open ends of which protrude about the
       water.
       [1913 Webster]

WordNet (r) 3.0 (2006):

hydraulic press
    n 1: press in which a force applied by a piston to a small area
         is transmitted through water to another piston having a
         large area